Electrical precipitator



United States Patent ELECTRICAL PRECIPITATOR Harry L. Richardson, Pittsburgh, Pa., assignor to Research gorfioration, New York, N. Y., a corporation of New Application March 16, 1953, Serial No. 342,359

3 Claims. (Cl. 183-7) This invention relates to electrostatic precipitators and in particular to an improved precipitator for treating gases at high pressures and also in some circumstances at high temperatures.

The trend in many modern industries is toward the utilization of high pressures and high pressures accompanied with high temperatures for reactions. In many of these there is a flowing gas stream either for trans port or reaction which requires treatment by electrostatic precipitator means.

This shift to high pressure and temperature reactions presents a major engineering difiiculty in application to electrostatic treatment of gases due to the lack of a satisfactory insulating seal which will allow high voltages to be conducted from atmospheric pressure to the interior of the precipitation apparatus operating at elevated pressures.

With presently available equipment it has been found impractical to operate electrostatic precipitators at pressures appreciably above the region of about 150 pounds per square inch. However, there is a substantial need for such equipment where it is desired to treat gas streams at pressures over 400 pounds and in some cases up to 1,000 pounds per square inch pressure.

In, addition to these high pressures, operating temperatures as high as 1000 F. may also be encountered, which is substantially above the operating levels of present types of precipitator equipment.

It is a principal object of the present invention to provide electrostatic precipitation equipment which can satisfactorily operate under the above described conditions.

It is a further object of the invention to provide such an apparatus that is efiicient in operation and may be operated under wide variations of pressures and temperature.

In general, these and other objects and advantages are accomplished by generating the high voltage at the pressure of the gases to be treated whereby it is only necessary to provide a high pressure seal for the low voltage which is readily accomplished by means well known in the art.

In installations where the gases to be treated are also at high temperatures the high voltage generating means may be either removed from the treatment chamber a sufiicient distance to permit normal atmospheric cooling of the high voltage generating equipment, or a coolant fluid provided with exteriorally-disposed refrigerating means may be employed.

The invention will be more particularly described with reference to the illustrative embodiments of the invention shown in the accompanying drawings in which:

Fig. 1 is a schematic diagram partly1 in section of an electrostatic precipitator embodying t e present invention;

Fig. 2 is an enlarged sectional view of the high voltage generator and'housing shown in Fig. 1; and

Fig. 3 is an enlarged detailed view of a preferred form of barrier between the electrical treatment and voltage generating chambers in accordance with the invention.

In the drawings, is the shell or casing of an electrical precipitator adapted for operation at high pressures and temperatures. The casing 10 is provided with a gas inlet 12 and a clean gas outlet 14. Within the casing and interposed between the gas inlet and outlet means is the gas cleaning apparatus which generally 2,705,544 Patented Apr. 5, 1955 ice comprises collecting electrodes 16 of conventional design and high voltage discharge electrodes 18.

The discharge electrodes are suspended from the upper end of the gas treating chamber from a high voltage bus bar 20. The bus bar 20 is in turn supported within the chamber on suitable high voltage ceramic insulators 22.

The high voltage for the discharge electrodes 18 is generated by the high voltage generating equipment generally designated 24 in high pressure chamber 26. The casing of chamber 26 is connected to the gas treating chamber by conduit 28, through which an extension 20' of the bus bar 20 passes. Within conduit 28 the bus bar extension 20 is provided with an insulating support 29. This insulator may be of standard design as it does not provide a gas seal between the gas treating chamber and the chamber 26. The casing 30 of chamber 26 is suitably connected to conduit 28 by welding or the like.

The high voltage generating equipment 24 as more clearly shown in Fig. 2 of the drawings comprising a closed tank 32 within which is a low voltage primary 34 and a high voltage secondary 36 of a suitable step-up transformer. Low voltage is brought to the primary windings of the transformer by conductors 38 which are brought out through seals 40 and 42 in tank 32 and casing 30.

The high voltage secondary 36 of the transformer is shown connected to a full wave rectifying circuit comprising, for example, selenium rectifiers 44 for the high tension side and similar rectifiers 46 for the grounded side of the circuit.

While only one cell is shown for the purpose of exemplification it will be understood that in practice there will be a stack of from ten to thirty cells depending upon the voltage of the transformer.

The high voltage lead 48 from the transformer is brought out through the cover of the tank 32 and through insulator 50 to the bus bar extension 20.

The rectifying apparatus and the transformer coils are both submerged in oil 52 contained in tank 32, and as hereinbefore described the high voltage generating equipment may be further cooled by a suitable cooling apparatus which is shown by way of example as coil 54 in the lower portion of the chamber 26. The leads 56 from the coil 54 can readily be brought out through the wall of casing 30 where they can be connected to a suitable refrigeration apparatus not shown in the drawing. On installations where the temperature between the gas treating chamber and the insulating oil 52 is very great, it may be desirable to surround the casing 26 with a thermal insulating jacket to improve the efficiency of operation of the temperature controlling element.

In some instances the gas to be treated may be corrosive or have other objectionable features, in which instances an inert gas can be supplied to chamber 26 through inlet pipe 58. The inert gas supplied through inlet 58 should be maintained at substantially the same pressure as exists,within the gas treating chamber or slightly higher. For this purpose a pressure balance regulator 60 may be provided to control an electrically activated valve 62 in inlet 58.

In instances where the inert gas cannot be tolerated in the gas treating chamber, a very small excess of pressure may be maintained in the gas treatment chamber. In either case it has been found that non-contamination may be enhanced by the provision of a specially constructed insulator 64 (see Fig. 3) in the conduit 28.

The insulator 64 is provided with a plurality of openings 66 which extend throughout the length of the insulator. These openings in the insulator permit breathing between chamber 26 and the gas treating chamber.

A filter mat 68 is provided at one or both ends of the insulator 64 which does not appreciably decrease the passage of gas through the openings 66 but prevents the passage of gas borne particulate matter. In cases where a large temperature difference exists between the treated gas and the temperature to be maintained in the high voltage generating chamber, the filter mat 68 may be constructed of a material having high thermal insulating and resistive properties, such as glass wool or porous ceramic material, whereby it will also serve to maintain the desired temperature difierence on both sides thereof.

From the foregoing description it will be seen that the present invention provides an improved electrostatic precipitation apparatus whereby the aims, objects and advantages of the invention are fully accomplished.

It will be evident that various modifications may be made in the form of the apparatus shown by way of example in the drawings; for example, where low temperature gases are to be treated the chamber 26 may be heated by means of the coils 54. It will also be evident since one of the advantages of the present invention is that electrical clearances may be reduced due to the high pressure surrounding the electrical equipment, a safety interlock comprising a pressure actuated switch 70 for the low voltage primary circuit may be advantageous. The switch 70 would be set to open that circuit wherever the pressure falls below a safe amount.

I claim:

1. Gas treating apparatus for operation under superatmospheric pressure comprising a gas treating chamber having a gas inlet and a gas outlet, complementary discharge and collecting electrode systems positioned in said gas treating chamber in the path of gas flow between said inlet and said outlet; a second chamber, means maintaining a superatmospheric pressure in said second chamber not substantially exceeding the superatmospheric pressure in the gas treating chamber, a stepup alternating current transformer and a rectifier for the high potential outlet of said transformer in said second chamber, a conduit connecting said chambers, and a high potential bus passing through said conduit and connecting the output of said rectifier with one of said electrode systems.

2. Gas treating apparatus for operation under superatmospheric pressure comprising a gas treating chamber having a gas inlet and a gas outlet, complementary discharge and collecting electrode systems positioned in said gas treating chamber in the path of gas flow between said inlet and said outlet; a second chamber, means maintaining a superatmospheric pressure in said second chamber slightly lower than the superatmospheric pressure in the gas treating chamber, a step-up alternating current transformer and a rectifier for the high potential outlet of said transformer in said second chamber, a conduit connecting said chamber, a high potential bus passing through said conduit and connecting the output of said rectifier with one of said electrode systems, an insulator for said bus in the conduit having openings therethrough for the passage of gas, and filter means in the openings in saidinsulator to prevent the passage of contaminating particular material from said gas treating chamber to said second chamber.

3. Gas treating apparatus as defined in claim 1 including means for supplying said second chamber with a gas different from the gasbeing treated, and means for maintaining the gas pressure in said chambers in said predetermined relation to each other.

References Cited in the file of this patent FOREIGN PATENTS 120,994 Great Britain Dec. 5, 1918 171,368 Great Britain May 18, 1922 500,545 Great Britain Feb. 8, 1939 550,850 Germany May 21, 1932 

1. GAS TREATING APPARATUS FOR OPERATION UNDER SUPERATMOSPHERIC PRESSURE COMPRISING A GAS TREATING CHAMBER HAVING A GAS INLET AND A GAS OUTLET, COMPLEMENTARY DISCHARGE AND COLLECTING ELECTRODE SYSTEMS POSITIONED IN SAID GAS TREATING CHAMBER IN THE PATH OF GAS FLOW BETWEEN SAID INLET AND SAID OUTLET; A SECOND CHAMBER, MEANS MAINTAINING A SUPERATMOSPHERIC PRESSURE IN SAID SECOND CHAMBER NOT SUBSTANTIALLY EXCEEDING THE SUPERATMOSPHERIC PRESSURE IN THE GAS TREATING CHAMBER, A STEPUP ALTERNATING CURRENT TRANSFORMER AND A RECTIFIER FOR THE HIGH POTENTIAL OUTLET OF SAID TRANSFORMER IN SAID SECOND CHAMBER, A CONDUIT CONNECTING SAID CHAMBERS, AND A HIGH POTENTIAL BUS PASSING THROUGH SAID CONDUIT AND CONNECTING THE OUTPUT OF SAID RECTIFIER WITH ONE OF SAID ELECTRODE SYSTEMS. 